Study on long-term pest control and stability of double-layer pesticide carrier in indoor and outdoor environment

Controlled-release pesticides are promising formulations for rice pest control. However, it is a big challenge for these formulations to sustainably and stably release pesticide in the soil at the whole process of crop growth. In this paper, based on chemical crosslinking of sulfonic acid group on sodium lignosulfonate (SL) with protonated UIO-66-NH2, we successfully construct a novel double-layer pesticide carrier to achieve the long-term pest control. Besides traditional indoor drug release, this work further investigates the release behavior in the soil column to simulate the outdoor environment. The results of release show that thiamethoxam (TMX)-loaded UIO-66-NH2/SL not only overcomes the shortage of burst release for natural polymer carriers in the soil, but also solves the problem that MOFs-based carrier is released too slowly in the early stage. Specifically, TMX-loaded UIO-66-NH2/SL has excellent biosafety and stability in outdoor environment. As a result, the rice treated by TMX-loaded UIO-66-NH2/SL is not affected by pests within 42 d, and the plant height of rice is up to 41 cm. In contrast, the rice treated by uncoated TMX is affected by pests at 16 d, and the plant height of rice is only 21 cm. Therefore, this study has developed a controlled-release pesticide that is more suitable for practical engineering applications.